Backflush valve

ABSTRACT

A backflush valve may open a traveling valve and a standing valve both at the same time so production tubing and a rod pump can be backflushed. The backflush valve may be adapted to connect to a pump barrel between the traveling valve and the standing valve and may be actuated by collapsing the pump.

FIELD OF THE INVENTION

The present invention relates to a backflush valve for a reciprocatingrod pump assembly and a method of backflushing a pump assembly.

BACKGROUND OF THE INVENTION

Reciprocating downhole pump systems are used to elevate productionfluids from an oil and gas well to the surface, A typical pump systemincludes a pump jack or other device at the ground surface thatreciprocates an attached sucker rod alternately in upstrokes anddownstrokes. The sucker rod is attached at its bottom end to a plungerthat reciprocates within a hollow pump barrel of a downhole pumpassembly. The plunger includes a travelling valve assembly, for examplea ball and seat valve or a flapper valve, to regulate the flow of aproduction fluid from below to above the plunger, while the pump barrelincludes a standing valve assembly to regulate the flow of theproduction fluid into the barrel from the producing perforations of awell, A retaining device such as a pump seating nipple is needed to holdthe barrel of the downhole pump assembly in a fixed position within theproduction tubing string as the travelling plunger moves up and down.

On the upstroke of the plunger, the travelling valve closes, so that theplunger lifts a column of production fluid in the pump barrel, upwardsin the production string, towards the ground surface. Simultaneously,the standing valve is opened so that the plunger draws additionalproduction fluid from the producing perforations of the well into thepump barrel below the plunger. On the downstroke of the plunger, thestanding valve closes to prevent the production fluid below the plungerfrom flowing back into the production tubing or well reservoir.Simultaneously, the pressure exerted by the production fluid in the pumpbarrel below the travelling valve forces the traveling valve to open.This allows the production fluid to flow into the pump barrel above theplunger and charges the pump barrel with a new column of productionfluid to be lifted on a subsequent upstroke.

On occasion, wax build up or a blockage due to solids build up impairspump operation. In these cases, it is desirable to backflush thedownhole pump assembly through the production tubing. However, thisconventionally requires unseating the pump from the pump seating nipplebecause the standing valve prevents reverse flow of fluid out of thepump barrel into the surrounding formation.

There is a need in the art for a device which would allow selectiveopening of the travelling and standing valves for a backflush operation.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a backflush valve to openthe traveling valve and the standing valve both at the same time so theproduction tubing and rod pump can be backflushed. In one embodiment,the backflush valve is adapted to connect to a pump barrel between atraveling valve and a standing valve, and comprises:

-   -   a. a hollow cylindrical housing having an upper end adapted to        connect to a pump barrel and a lower end adapted to connect to a        standing valve assembly comprising a standing valve ball and        valve seat;    -   b. a push rod disposed and centralized within the housing, the        push rod having an upper end and a lower end, wherein the lower        end comprises a ball wedge;    -   c. wherein the push rod may reciprocate within the housing from        a relaxed position where the ball wedge is positioned away from        the standing ball valve to a deployed position where the ball        wedge displaces the standing ball valve off the standing valve        seat;    -   d. a spring contained within the housing and acting on the push        rod to bias into its relaxed position.

In one embodiment, the push rod is centralized by at least onecentralizing insert defining at least one flow passage.

In another aspect, the invention may comprise a method of backflushing areciprocating pump assembly having a backflush valve adapted to connectto a pump barrel between a traveling valve and a standing valve, thebackflush valve comprising a centralized pushrod having an upper end anda lower end comprising a ball wedge, comprising the steps of

-   -   a. collapsing the pump such that the traveling valve falls and        contacts the push rod, thereby opening the traveling valve; and    -   b. urging the push rod downwards such that the ball wedge        contacts the standing valve ball, displacing it off the standing        valve ball seat.

In one embodiment, the traveling valve comprises a traveling valve ballwhich contacts the push rod to push it downwards.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of an exemplary embodimentwith reference to the accompanying simplified, diagrammatic,not-to-scale drawings. Any dimensions provided in the drawings areprovided only for illustrative purposes, and do not limit the inventionas defined by the claims. In the drawings:

FIG. 1 is a sectional view of a reciprocating downhole pump systemincorporating one embodiment of the backflush valve of the presentinvention;

FIG. 2 is a cut-away sectional view of a one embodiment of the backflushvalve of FIG. 1;

FIG. 3 is a partial cut-away view of one embodiment of the push rod andcentralizing inserts of one embodiment of the present invention; and

FIG. 4 is a view of the embodiment of FIG. 3, in a disassembled state.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a backflush valve for facilitating abackflush process of a downhole pump assembly in a production tubingstring. When describing the present invention, all terms not definedherein have their common art-recognized meanings. To the extent that thefollowing description is of a specific embodiment or a particular use ofthe invention, it is intended to be illustrative only, and not limitingof the claimed invention. The following description is intended to coverall alternatives, modifications and equivalents that are included in thespirit and scope of the invention, as defined in the appended claims.

As used herein, the term “up” or “upwards” refers to the direction ofthe surface end of the well, while “down” or “downwards” refers to thedirection towards the bottom or toe end of the well. These referencesare intended to describe the relative orientation or direction ofmovement of components, and not to describe the actual orientation ofthe components at any time. As one skilled in the art will understand,the downhole pump assembly may be installed in any position between avertical or a horizontal orientation.

In one aspect, the present invention provides a backflush valve (10)adapted to connect to a pump barrel (B) between a traveling valve (T)and a standing valve (S), the backflush valve comprising:

-   -   a. a hollow cylindrical housing (12) having an upper end adapted        to connect to the pump barrel and a lower end adapted to connect        to the standing valve assembly (S) comprising a standing valve        ball (B) and valve seat (SVS);    -   b. a push rod (14) disposed and centralized within the housing,        the push rod having an upper end (16) and a lower end (18),        wherein the lower end comprises a ball wedge (20);    -   c. wherein the push rod (14) may reciprocate within the housing        (12) from a relaxed position where the ball wedge (20) is        positioned away from the standing ball valve to a deployed        position where the ball wedge (20) displaces the standing ball        valve off the standing valve seat;    -   d. a spring (22) contained within the housing and acting on the        push rod to bias it into its relaxed position.

In one embodiment, the push rod is centralized by at least onecentralizing insert (24) defining at least one flow passage. As shown inthe Figures, in a preferred embodiment, two centralizing inserts (24)fit onto the push rod, and have an outside diameter closely matching theinside diameter of the housing (12). Each insert (24) defines peripheralflow passages and each insert defines a spring cavity (26). An alignmentpin (28) which inserts into the centralizing inserts ensures theperipheral flow passages are aligned when the device (10) is assembled.The inserts (24) are retained in place between opposing seats (30, 32)defined by the inside of the housing. For ease of assembly, the housingmay comprise two halves which attach together, for example, by athreaded connection.

The spring (22) acts between the lower portion of the lower insert (24)and a pin (34) affixed to the push rod (14).

In normal pump operation, the push rod (14) is in its relaxed position,and production fluid flows through the backflush valve without unduerestriction. The upper end (16) of the push rod may be used incombination with a gas locking relief device (not shown) such as thatdescribed in co-owned U.S. application Ser. No. 13/583,667 entitledDownhole Gas Release Apparatus, the entire contents of which isincorporated herein by reference, where permitted. In this case, anadapter (40) may be fitted to the upper end of the push rod, tofacilitate its interaction with a gas locking relief device.

A nut (not shown) or stop formed on the pushrod may be used to limittravel of the pushrod by bearing on the top of an insert (24). Too muchforce on the pushrod may bend the rod, or damage the standing valve.

When installed in a downhole pump assembly and during production, thebackflush valve (10) does not influence either the traveling valve orthe standing valve. Production fluid bypasses the valve (10) through theflow passages. In a backflush operation, the pump is collapsed byletting the sucker rods fall to the bottom. As a result, the travelingvalve falls toward its lowest point, and the traveling valve ballcontacts the top of the push rod (14), either directly or indirectly,and is thus unseated. The traveling valve then urges the push rod (14)downwards, compressing the spring (22) as shown in FIG. 3, and movingthe ball wedge (20) into contact with the standing valve ball,displacing it off the standing valve ball seat.

As a result, the production tubing and pump assembly is now entirelyopen to the formation, and a fluid may be backflushed through theproduction tubing and the rod pump, without unseating the pump barrel.

As will be apparent to those skilled in the art, various modifications,adaptations and variations of the foregoing specific disclosure can bemade without departing from the scope of the invention claimed herein.

What is claimed is:
 1. A backflush valve adapted to connect to a pumpbarrel between a traveling valve and a standing valve, and comprising:a. a hollow cylindrical housing having an upper end adapted to connectto a pump barrel and a lower end adapted to connect to a standing valveassembly comprising a standing valve ball and valve seat; b. a push roddisposed and centralized within the housing, the push rod having anupper end and a lower end, wherein the lower end comprises a ball wedge;c. wherein the push rod may reciprocate within the housing from arelaxed position where the ball wedge is positioned away from thestanding ball valve to a deployed position where the ball wedgedisplaces the standing ball valve off the standing valve seat; d. aspring contained within the housing and acting on the push rod to biasinto its relaxed position.
 2. The backflush valve of claim 1 wherein thepush rod is centralized by at least one centralizing insert insertedinto the housing and defining at least one flow passage.
 3. Thebackflush valve of claim 2 comprising two centralizing inserts, togetherdefining a spring cavity for retaining the spring.
 4. The backflushvalve of claim 3 further comprising an alignment pin which aligns thetwo centralizing inserts to align their at least one flow passages. 5.The backflush valve of claim 1 wherein an upper end of the push rod isadapted to engage a gas locking relief device.
 6. A method ofbackflushing a reciprocating pump assembly having a backflush valveadapted to connect to a pump barrel between a traveling valve and astanding valve, the backflush valve comprising a pushrod having an upperend and a lower end comprising a ball wedge, comprising the steps of: a.collapsing the pump such that the traveling valve falls and contacts thepush rod, thereby opening the traveling valve; and b. urging the pushrod downwards such that the ball wedge contacts the standing valve ball,displacing it off the standing valve ball seat.
 7. The method of claim 6wherein the pushrod is centralized by a centralizer within a housing,the centralizer defining at least one flow passage.
 8. The method ofclaim 7 wherein the pushrod is upwardly biased within the housing. 9.The method of claim 8 wherein the backflush valve comprises twocentralizing inserts, together defining a spring cavity for retaining aspring which biases the pushrod upwards.